1. Field of Invention
The present invention pertains to a paper separator for separating paper from a photosensitive body or bodies and to a processor cartridge provided therewith for use in copiers and other such electrophotographic image forming apparatuses.
2. Conventional Art
Typical constitutions for electrophotographic image forming apparatuses include, for example, those such as copier 1 shown in FIG. 13 (see Japanese Patent Application Publication Kokai No. H6-27753 (1994)). This copier 1 is equipped with an optical system 10, by means of which an original stage 101 (glass platen) is irradiated with light, light reflected therefrom exposing a photosensitive body 110 by way of mirrors 102 and a lens 103; a developer apparatus 111, a transfer apparatus 112, a cleaning apparatus 113, and a charging apparatus 114, which are arranged about the photosensitive body 110; a fuser apparatus 120, which fuses toner transferred onto paper from the photosensitive body 110; a discharge tray 130, which receives paper from this fuser apparatus 120; and a supply apparatus 140, which supplies paper to the photosensitive body 110.
In accordance with this constitution, paper within the storage cassette 141 is supplied by a supply roller 142, is guided by a U-turn guide 143, and is carried by transport rollers 144 to a point just short of control rollers 145 (PS roller).
In addition, in synchronous fashion therewith, the original on the original stage 101 is exposed to light which then travels along an optical path represented by the mirrors 102 and the lens 103 to form an image on the photosensitive body 110 through an electrostatic process, and the electrostatic image formed on the photosensitive body 110 is made into a toner image by the developer apparatus 111.
Furthermore, in order to cause the paper, which had previously stopped in front of the control roller 145, to be made to lie directly over the foregoing toner image, the control roller 145 is made to rotate together with the rotation of the photosensitive body 110, causing the paper to be transported onto the surface of the photosensitive body 110. In addition, a high-voltage charge produced by the transfer apparatus 112 acts from the back of the paper which lies against the photosensitive body 110 and causes the toner image on the photosensitive body 110 to be transferred to the paper. At such time, due to the high-voltage charge which has been applied to the paper, the paper clings electrostatically to the surface of the photosensitive body 110; and in order to separate this therefrom, a paper separator 150 is provided at a point downstream from the transfer apparatus 112 in the direction of rotation of the photosensitive body 110. Note that at FIG. 13, reference numerals 146 and 147 represent guide plates for paper transport.
This paper separator 150 is equipped with a plurality of paper-separating fingers 151, . . . , abutting and/or backed off from photosensitive body 110, for separating paper therefrom. Each paper-separating finger 151 has finger body or bodies at or near the upstream end thereof in the paper transport direction which is or are capable of abutting photosensitive body 110, such finger body or bodies being urged to abut the photosensitive body 110 as a result of restoring force(s) from spring(s). In addition, the paper-separating fingers 151 are connected to solenoid(s) by way of a plurality of clutch mechanisms and are supported so as to allow movement in direction(s) of engagement and retraction such that driving of the solenoid(s) in synchronous fashion with respect to the control roller 145 causes finger body or bodies to at least partially overcome restoring force(s) of spring(s) and back off from the photosensitive body 110.
Furthermore, other examples of paper separators include those in which paper-separating finger(s) are operated so as to be brought into and out of abutting engagement with photosensitive body or bodies as a result of merely turning solenoid(s) ON and OFF, operations for bringing paper-separating finger(s) into and out of abutting engagement with photosensitive body or bodies being such that turning ON and OFF of solenoid(s) is controlled based on processing speed, installation conditions such as humidity and temperature, and the relative tendency for paper to separate from photosensitive body or bodies as determined by type of paper (see, e.g., Japanese Patent Application Publication Kokai No. H14-108110 (2002)).
However, the paper separators described above respectively possess deficiencies such as the following.
To wit, in the first of the two types of paper separator described above, where spring(s) are used to make finger body or bodies of the paper-separating fingers 151 abut the photosensitive body 110, because restoring force(s) from spring(s) cause finger body or bodies to press firmly against the photosensitive body 110, the surface of the photosensitive body 110 become scratched, leading to deterioration of the photosensitive body 110. Even where such effect of paper-separating fingers does not represent a problem while the photosensitive body 110 is in its initial state, there is no disputing that the effect thereof on images will become apparent with continued use, leading to decrease in quality of the images formed therewith. Moreover, special-purpose solenoids are required for operating paper-separating fingers so as to bring them into and out of abutting engagement with photosensitive body or bodies, making increase in the size of the paper separator unavoidable.
Furthermore, in the second of the two types of paper separator described above, where the turning ON and OFF of solenoids is controlled, control circuits are required for accurate timing with respect to turning ON and OFF of solenoids, in order to carry out control based on processing speed, installation conditions, and relative tendency for paper to separate from photosensitive body or bodies, increasing cost. Moreover, where solenoids are used for operations causing paper-separating finger(s) to come into and out of abutting engagement with photosensitive body or bodies, because such operations themselves require a certain amount of time after the start of paper transport, in instances where a multifeed event has occurred at the supply unit (referring to a situation in which the leading edge of a subsequently transported sheet of paper is dragged along by a previously transported sheet of paper, causing it to move to a location forward of its normal position) or where intervals between successive sheets grow small due to slippage of transport rollers or the like, it is difficult to compensate for same by controlling solenoids, contributing to occurrence of jams.